Kangaroo Grazing Research Articles

Comparing grass biomass estimation methods for management decisions in a semi‐arid landscape

AbstractAimsEnvironmental managers require reliable and cost‐efficient monitoring methods for effective decision‐making. Understanding forage availability is important for managing wild, vertebrate herbivore populations. We developed a process for exploring the accuracy and cost efficiency of various biomass estimation techniques for a case study where semi‐arid woodland restoration is threatened by kangaroo grazing, with the aim of determining which method was most fit for purpose in a given decision context.LocationWyperfeld National Park, southeastern Australia.MethodsGrass biomass was estimated using a variety of methods, then compared to clipped biomass using linear models. Biomass estimation methods were either field‐based (i.e., rising plate meter, multispectral radiometer) or satellite‐based (i.e., Landsat satellite imagery, AussieGRASS forage production model). Sampling occurred across open and wooded semi‐arid vegetation types. We compared methods based on accuracy, the ability of each method to accurately predict a ‘forage‐switch’ threshold, cost, and the suitability for the management context.ResultsFor this case study, the multispectral radiometer was the most precise, yet most expensive, biomass estimation method over a single survey. However, satellite imagery proved to be the most cost‐efficient and fit for purpose, as it was inexpensive and most accurately estimated biomass around a forage‐switch threshold, second only to the multispectral radiometer. Accuracy of all methods was improved by including tree cover in the regression models.ConclusionsWe demonstrate a process for exploring which biomass estimation tool might be preferred for a given decision context, highlighting accuracy, consideration of tolerance to uncertainty and risk, the spatial and temporal scale of information required, and budget constraints.

Understanding the spatiotemporal dynamics of understorey biomass in semi-arid woodlands of south-eastern Australia

When managing grazing pressure for conservation, understanding forage dynamics is essential. In south-eastern Australia, ongoing grazing is inhibiting regeneration in several semi-arid woodland communities. Western grey kangaroos (Macropus fuliginosus (Desmarest, 1817)) have been identified as a key component of total grazing pressure. They are thought to switch from grass to lower-quality browse, including tree seedlings, when grass biomass falls below 400 kg ha−1. One static threshold may not adequately capture the spatial and temporal hazard associated with kangaroo grazing, and this study aimed to explore how grassy biomass varies across a case-study landscape. Understorey biomass and species composition data were collected in the field on seven occasions between December 2016 and May 2019. We used Generalised Linear Mixed Models (GLMMs) to describe the influence of environmental and herbivory variables on total (live and dead) understorey, live understorey, and grass (live and dead) biomass. Canopy cover showed the strongest influence on understorey biomass, with more biomass found in open sites than in woodland. Understorey biomass levels were lowest in summer and autumn. Grass biomass, in particular, fell below the 400 kg ha−1 forage-switch threshold in wooded areas during this time. We anticipate that an increased understanding of understorey biomass dynamics will inform managers as to when and where to focus management efforts to promote regeneration and sustained recovery of these semi-arid woodlands. Results of this study suggest that conducting management efforts before the summer/autumn decline in understorey biomass, particularly in woodlands, is critical in reducing the browsing risk to seedlings.

Kangaroos, drought and a frustrated landowner

Kangaroos, drought and a frustrated landowner

Impacts of grazing by kangaroos and rabbits on vegetation and soils in a semi-arid conservation reserve

Overgrazing by introduced herbivores is widely recognized as a threatening process in Australia's semi-arid rangelands. Comparatively, grazing by native herbivores is generally considered to have benign effects. Populations of introduced herbivores are controlled in conservation reserves, but populations of native kangaroos and wallabies are seldom subject to control. We investigated the impacts of rabbit and kangaroo grazing on vegetation and soils at Yathong Nature Reserve in semi-arid Australia during the dry conditions that prevailed in 2019. We conducted spotlight and dung surveys to measure the relative abundance of kangaroos and rabbits, and assessed understorey biomass, woody plant density, soil bulk density and water infiltration rates in selective herbivore exclosures that had been established in 1979, and nearby controls that all herbivores could access. Kangaroos were the dominant herbivores at the time of our study. Grazing by kangaroos decreased grass biomass, increased soil density and reduced the rate of water infiltration. Rabbits reduced woody plant density but had no detectable effect on understorey vegetation cover or soil attributes. Our findings question the existing paradigms about how grazing by kangaroos should be viewed and prompt the question: should kangaroo populations be managed within conservation reserves to reduce their impacts on ecosystems?

Low‐intensity kangaroo grazing has largely benign effects on soil health

SummaryKangaroos (Macropus spp., Osphranter spp.) are the most ubiquitous free‐ranging herbivores in Australia. Much has been written on their impacts on plant community composition and how they interact with livestock, particularly in extensive rangelands. Little is known, however, about how kangaroos affect soil function and their relationship with healthy soils, nor the impact of peri‐urban populations of kangaroos where they might come into conflict with humans. To address this, we used exclosures to examine the impacts of low densities of kangaroos on the morphology of the soil surface in a peri‐urban environment on the outskirts of Sydney, Australia. We found that kangaroo grazing was associated with reduced herbaceous biomass and cover, and biocrust cover, and surfaces were generally more stable, had a greater cover and incorporation of litter and had greater plant species richness compared to inside the exclosures. There were no differences in indices of nutrient cycling nor stability. Overall, our study supports the notion that kangaroo grazing, at the current low densities experienced in this peri‐urban reserve, has had no significant deleterious effect on soil surface health, as measured by the morphology of the surface. We conclude that grazing at the current low levels (˜70 kangaroos km−2) is unlikely to have major long‐term negative effects on soil surface condition.

Livestock and kangaroo grazing have little effect on biomass and fuel hazard in semi-arid woodlands

Using livestock grazing as a tool to manage biomass and reduce fuel hazard has gained widespread popularity, but examples from across the globe demonstrate that it often yields mixed, context-dependent results. Grazing has potential to deliver practical solutions in systems where grazing reduces not only biomass but also reduces fuel hazard by altering vegetation connectivity or composition. We assessed the extent to which recent rainfall, rabbit and kangaroo grazing and recent and historic livestock grazing alters and accounts for variation in above-ground biomass, biomass composition and fuel hazard ratings across three broad communities in eastern Australia. We used nested linear models to assess biomass in three vertical vegetation strata, that matched the strata assessed in the Overall Fuel Hazard Assessment guide (i.e. litter/surface fuel; groundstorey vegetation/near surface fuel; and midstorey vegetation/elevated fuel) and Ordinal Logistic Regression to assess categorical fuel hazard ratings. Only recent kangaroo grazing reduced groundstorey biomass across all communities. Kangaroo grazing altered litter mass and significantly reduced surface fuel hazard in one community. Recent livestock grazing did not reduce fuel hazard, and despite significantly reducing half of our measures of biomass, these were not practical reductions. For instance, livestock grazing significantly reduced litter mass, however our model predicts that doubling our assessment of livestock grazing intensity only reduces total litter mass by 0.8%, or 8 kg per hectare in landscapes where average litter loads ranged from 3600 to 12,600 kg per hectare. Furthermore, long-term livestock grazing increased shrub biomass and in one community this increased elevated fuel hazard. There were few effects of rabbits. The effects of rainfall on biomass were up to an order of magnitude greater than any effects due to grazing, despite sampling during relatively average rainfall conditions. Our data suggest that management practices that seek to use livestock grazing to reduce biomass or its connectivity in these systems will not achieve practical reductions in biomass and or fuel hazard.

Grazing and productivity alter individual grass size dynamics in semi‐arid woodlands

The spatial arrangement of perennial vegetation is critical for ecosystem function in drylands. While much is known about how vegetation patches respond to grazing and abiotic conditions, the size dynamics of individual plants is mostly limited to theoretical studies. We measured the size distribution (mean, variance, skewness) and density of individual grasses, and grass species composition at 451 sites spanning a range of grazing intensities across three broad vegetation communities in semi‐arid eastern Australia. We assessed the relative role of grazing by livestock (cattle and sheep), native (kangaroos) and introduced (rabbits) free ranging herbivores, and several environmental measures (productivity, diversity, composition and groundstorey plant cover) on the size distribution and density of individual grasses. We found mean grass size and density were more sensitive to shifts in grazing intensity and environmental conditions than size variance or the frequency of the smallest individuals (skewness), and shifts were mostly driven by site productivity and cattle and kangaroo grazing. Sheep grazing only reduced mean grass size, and rabbit grazing had no consistent effects. Importantly, we found that site productivity and species composition altered the impacts of grazing on grass density and size distribution. For example, increasing cattle grazing led to larger grasses in low productivity sites. It also led to larger, denser, more variable‐sized grasses among grass species from sites with finer soil texture. Increasing kangaroo grazing led to smaller, denser individuals among grass species from sites with coarse soil texture. At high diversity sites kangaroo grazing led to denser, more homogenised grass sizes with a lower frequency of small individuals. Understanding the in situ response of individual plant sizes gives us insights into the processes driving shifts in perennial vegetation patchiness, improving our ability to predict how the spatial arrangement of ecosystems might change under global change scenarios.

Returning a lost process by reintroducing a locally extinct digging marsupial.

The eastern bettong (Bettongia gaimardi), a medium-sized digging marsupial, was reintroduced to a predator-free reserve after 100 years of absence from the Australian mainland. The bettong may have the potential to restore temperate woodlands degraded by a history of livestock grazing, by creating numerous small disturbances by digging. We investigated the digging capacity of the bettong and compared this to extant fauna, to answer the first key question of whether this species could be considered an ecosystem engineer, and ultimately if it has the capacity to restore lost ecological processes. We found that eastern bettongs were frequent diggers and, at a density of 0.3–0.4 animals ha−1, accounted for over half the total foraging pits observed (55%), with echidnas (Tachyglossus aculeatus), birds and feral rabbits (Oryctolagus cuniculus) accounting for the rest. We estimated that the population of bettongs present dug 985 kg of soil per ha per year in our study area. Bettongs dug more where available phosphorus was higher, where there was greater basal area of Acacia spp. and where kangaroo grazing was less. There was no effect on digging of eucalypt stem density or volume of logs on the ground. While bettong digging activity was more frequent under trees, digging also occurred in open grassland, and bettongs were the only species observed to dig in scalds (areas where topsoil has eroded to the B Horizon). These results highlight the potential for bettongs to enhance soil processes in a way not demonstrated by the existing fauna (native birds and echidna), and introduced rabbit.

Horse Activity is Associated with Degraded Subalpine Grassland Structure and Reduced Habitat for a Threatened Rodent

Feral (wild) horses present significant challenges for landscape managers. A major effect of horses is trampling, which erodes soil and alters vegetation cover, which is often critical habitat for threatened animals. We examined the direct and indirect impacts of horses, kangaroos, and rabbits on the broad-toothed rat (Mastacomys fuscus), a threatened rodent in subalpine grasslands in Kosciusko National Park, which contains a large wild horse population. Our objective was to examine the relationship between the activity of different herbivores and 1) structural attributes of the vegetation (cover and density of different plant groups) and 2) length of broad-toothed rat runways and the presence of scat along these runways as proxies of broad-toothed rat activity. We assessed herbivore activity and measured vegetation cover, structure, and richness and total length of runways used by broad-toothed rats as a measure of activity. We used structural equation modeling to test the hypothesis that horse activity would lead to reductions in rat habitat directly, by increasing disturbance, and indirectly, by altering vegetation structure. Quadrats showing no evidence of horse activity had longer broad-toothed rat runways, taller but fewer grasses, double the shrub cover, and lower plant richness than quadrats showing evidence of horse activity. Structural equation modeling showed that there were no significant direct associations between horse activity and rat activity. However, increasing horse activity was associated with an indirect negative effect on broad-toothed rat activity by suppressing the positive relationship between grass height and rat activity. There were no significant effects of rabbits on any environmental variables, and kangaroo grazing was associated with an increase in shrub cover only. Disturbance by horses likely alters vegetation structure, by reducing grass height, making it less suitable for broad-toothed rats, thereby reducing their populations. Horses should be restricted from accessing critical broad-toothed rat habitat.

Recent grazing reduces reptile richness but historic grazing filters reptiles based on their functional traits

Abstract Grazing by mammalian herbivores can alter vegetation structure and composition. It can therefore affect critical habitat features used by native wildlife for shelter, feeding, and breeding. This can have variable effects, which advantage or disadvantage particular species, depending on habitat requirements. We tested the relative effects of recent and historic livestock grazing and recent rabbit and kangaroo grazing on all reptiles, and on specific groups of reptiles based on three functional traits: habitat preference (semi‐arboreal, terrestrial, fossorial), activity pattern (diurnal, nocturnal), and primary foraging habitat (tree, litter, open). We used structural equation modelling to assess the direct and indirect impacts of mammalian herbivores (livestock, and free‐ranging kangaroos and rabbits) on reptile richness at 108 semi‐arid woodland sites in eastern Australia. We used a trait‐based approach to classify reptiles according to their: (a) habitat preference, (b) activity pattern, and (c) foraging preference. We recorded 42 reptile species from 1,736 specimens caught over 13,824 trap nights. Sites grazed by rabbits were associated with greater richness of semi‐arboreal species. Kangaroo grazing had virtually no effects on total richness or richness within trait groups. The effects of recent and historic livestock grazing differed among reptile trait groups. Increasing intensity of recent livestock grazing reduced the richness of most reptile groups directly, and indirectly suppressed the positive effect of native plant richness on reptile richness. The effects of historic livestock grazing, however, filtered reptiles based on their traits, reducing the richness of tree‐shrub foraging reptiles only. Increasing woody cover had direct suppressive effects on all reptiles, but particularly open foragers and terrestrial species. Overall, the effects of recent livestock grazing were stronger than those of plant richness or woody cover. Synthesis and applications. We demonstrate how grazing by all herbivores, both domestic and free‐ranging, needs to be managed according to seasonal conditions in order to meet the conservation needs of semi‐arid reptiles within landscapes dominated by livestock.

Introduced and native herbivores have different effects on plant composition in low productivity ecosystems

AbstractQuestionsUnderstanding how livestock grazing alters plant composition in low productivity environments is critical to managing livestock sustainably alongside native and introduced wild herbivore populations. We asked four questions: (1) does recent livestock and rabbit grazing reduce some plant attributes more strongly than others; (2) does grazing by introduced herbivores (i.e. livestock and rabbits) affect plants more strongly than native herbivores (i.e. kangaroos); (3) do the effects of recent livestock grazing differ from the legacy effects of livestock grazing; and (4) does the probability of occurrence of exotic plants increase with increasing net primary productivity (NPP)?LocationSouth‐eastern Australia.MethodsWe measured the recent grazing activity of co‐occurring livestock (cattle, sheep, goats), rabbits and kangaroos by counting faecal pellets; historic grazing activity by measuring livestock tracks; and derived NPP from satellite imagery. We used a hierarchical GLMM to simultaneously model the presence or absence (i.e. probability of occurrence) of all plant species as a function of their attributes (growth form, lifespan and origin) to assess their average response to recent grazing, historic grazing and productivity in a broad‐scale regional study.ResultsRecent and historic livestock grazing, rabbit grazing and increasing NPP reduced the average probability of occurrence of plant species, although responses varied among plant attributes. Both recent and historic livestock grazing strongly reduced the average probability of occurrence of native species, and forbs and geophytes, but differed in their relative effects on other growth forms. Recent livestock grazing, rabbit grazing and NPP had similar effects, strongly reducing native species and forbs, geophytes, shrubs and sub‐shrubs. The overall effects of recent kangaroo grazing were relatively weak, with no clear trends for any given plant attribute.ConclusionOur results highlight the complex nature of grazing by introduced herbivores compared with native herbivores on different plant attributes. Land managers need to be aware that domestic European livestock, rabbits and other free‐ranging introduced livestock such as goats have detrimental impacts on native plant communities. Our results also show that kangaroo grazing has a relatively benign effect on plant occurrence.

Livestock activity increases exotic plant richness, but wildlife increases native richness, with stronger effects under low productivity

Abstract Grazing by domestic livestock is one of the most widespread land uses world‐wide, particularly in rangelands, where it co‐occurs with grazing by wild herbivores. Grazing effects on plant diversity are likely to depend on intensity of grazing, herbivore type, co‐evolution with plants and prevailing environmental conditions. We collected data on climate, plant productivity, soil properties, grazing intensity and herbivore type, and we measured their effects on plant species richness from 451 sites across 0.4 M km2 of semi‐arid rangelands in eastern Australia. We used structural equation modelling to examine the direct and indirect effects of increasing grazing intensity by different herbivores (cattle, sheep, kangaroos, rabbits) on native and exotic plant species richness across all sites, and in subsets focusing on three woodland communities spanning a gradient in productivity. Direct effects of grazing by all herbivores were strongest under low productivity but waned with increasing productivity. Increases in the intensity of recent and historic livestock grazing corresponded with greater exotic plant richness under low productivity and less native plant richness under both low and moderate productivity. Rabbit effects were greatest under moderate productivity. Overall, the effects of kangaroos were benign. Grazing indirectly affected native and exotic plant richness by increasing soil phosphorus and reducing soil health (i.e. nutrient cycling). Synthesis and applications. Our study shows that livestock grazing increases exotic species richness but reduces native richness, while kangaroo grazing increases native richness in environments with low productivity. The results provide clear messages for land managers and policy makers: (1) the coexistence of livestock grazing and plant diversity is only possible within more productive environments and (2) grazing under low or moderate productivity will impact upon native and exotic plant richness.

Trajectories of floristic change in grassland: landscape, land use legacy and seasonal conditions overshadow restoration actions

AbstractQuestionsHow does ground‐layer plant composition respond to the imposition of woodland habitat restoration treatments following the removal of long‐term pastoral management? Do different vegetation types have different trajectories of change?LocationA long‐term ecological research site comprising temperate eucalypt grassy woodland and forest in south‐eastern Australia, converted from pastoral use to conservation management. This has involved the implementation of habitat restoration treatments in addition to the cessation of livestock grazing and fertilizer inputs.MethodsWe surveyed ground‐layer floristic composition over a 4‐yr interval, in 96 1‐ha sites that had been subjected to combinations of restoration treatments aimed at improving the condition of the woodland habitat for fauna: (1) Reduced kangaroo grazing intensity; (2) Addition of coarse woody debris; and (3) Burning. We used nonmetric multidimensional scaling (NMDS) to plot the sites, and to analyse the average trajectories of floristic change for each of six initially identified vegetation types, and the restoration treatments. We partitioned Bray–Curtis dissimilarity measures to rank individual species’ contributions to floristic change in each vegetation type between 2007 and 2011.ResultsThe identities of the six vegetation types identified at time zero was strongly retained over the 4‐yr observation period. There was generally a uniform change across the vegetation types, which was the result of increases in biomass of the characteristic dominant perennial grasses, and increases in some native forbs. The two vegetation types with evidence of past fertilization showed some convergence with native vegetation types due to the decrease in some exotic species. The restoration treatments had no significant influence on species composition.ConclusionsThe native herbaceous vegetation in the woodland was largely resistant to compositional change, although seasonal conditions increased the biomass of the perennial grasses defining the different vegetation types. However, sites with an evident history of past fertilization and notable amounts of exotic pasture species changed slightly but significantly, with some pasture species declining and floristic convergence with native vegetation over 4 yr. These rates of change need to be considered in the application of vegetation offsetting policy.

In the absence of an apex predator, irruptive herbivores suppress grass seed production: Implications for small granivores

Many examples exist of species disappearing shortly after the extinction of a previously co-occurring apex predator, however processes connecting these events are often obscure. In Australian deserts, dingo Canis dingo eradication is associated with declines in abundances of small granivorous birds, even though dingoes and these flying birds rarely directly interact. We hypothesised that dingoes facilitate small granivores by reducing populations of large, grazing kangaroos Macropus spp., thereby increasing grass seed production and availability. To test this prediction, we monitored kangaroo abundances and surveyed grass seed production and biomass of native pastures in matched, desert habitats with dingoes and where dingoes were functionally extinct. Dingo absence was associated with 99.9% greater abundances of kangaroos, 88% - 98% lower pasture biomasses and 85% - 97% lower densities of grass seed heads. To test that these vegetation effects were related to kangaroo grazing, we constructed large herbivore exclosures in areas where dingoes where functionally extinct and there were no grazing livestock. After three years of kangaroo exclusion, pasture biomass and grass seed production were each 87% greater than in adjacent, grazed control plots. Regeneration of vegetation within the kangaroo exclosures demonstrated that kangaroo grazing was responsible for the differences in native pastures we had observed associated with the functional extinction of dingoes. Our results indicate that reduction of grass seed availability by kangaroo grazing is a likely explanation for the relative rarity of small granivorous birds in areas where dingoes are functionally extinct. In areas where apex predators have been eradicated, reintroducing and conserving apex predators or intensively controlling mammalian herbivores would be necessary to mitigate destructive herbivory.

Contrasting Effects of Aridity and Grazing Intensity on Multiple Ecosystem Functions and Services in Australian Woodlands

AbstractGlobal change is expected to reduce the provision of multiple ecosystem services in drylands, the largest biome on Earth. Understanding the relative importance of climate change and overgrazing on ecosystems services is critical for predicting the effects of global change on ecosystem well‐being. We generated a system‐level understanding of the effects of climate (aridity intensity) and land use intensification (herbivore grazing intensity) on four regulating ecosystem services (C‐storage, N‐availability and P‐availability, and organic matter decomposition) and one provisioning service (plant production) in wooded drylands from eastern Australia. Climate change and grazing intensity had different effects on multiple ecosystem services. Increasing aridity from 0·19 (dry subhumid) to 0·63 (arid) had consistent suppressive effects on C‐storage, N‐availability, decomposition and plant biomass services, but not on P‐availability. The magnitude of these suppressive effects was greater than any effects due to grazing. All sites showed evidence of kangaroo grazing, but the heaviest grazing was due to cattle (dung: range 0–4545 kg ha−1; mean 142 kg ha−1). Any effects of grazing on ecosystem services were herbivore specific and ranged from positive to neutral or negative. Sheep, and to a lesser extent cattle, were associated with greater N‐availability. Rabbits, however, had a greater effect on P‐availability than aridity. Our study suggests that increases in livestock grazing may fail to sustain ecosystem services because of the generally stronger negative effect of increasing aridity on most ecosystem services in our model dryland. These services are likely therefore to decline with global increases in aridity. Copyright © 2017 John Wiley & Sons, Ltd.

Density-dependent grazing impacts of introduced European rabbits and sympatric kangaroos on Australian native pastures

Little information is available on relationships between pest animal density and damage in natural ecosystems. Introduced European rabbits, Oryctolagus cuniculus, cause severe damage to Australian native vegetation but density–damage relationships are largely unexplored. There are no recognized simple methods to estimate their impacts on native pastures, due in part to confusion with grazing impact of other herbivores. We tested simple quantitative sampling methods using multiple small quadrats to detect site differences in pasture cover, pasture species richness and dung pellet density of herbivores, from which rabbit density and relative abundance of larger herbivores were estimated. Native pasture cover and species richness declined exponentially with increasing rabbit density, within the range of 0–5 rabbits ha−1, while cover of unpalatable exotic pasture species increased. By contrast, kangaroo abundance was positively related to palatable native pasture cover and negatively related to cover of unpalatable weeds, and had no negative effect on native pasture cover or species richness that was discernable against a background of low to moderate rabbit densities. Perennial native forbs and perennial grasses replaced invasive Wards weed as the dominant ground cover at low rabbit densities. We conclude that, regardless of previous grazing history, contemporary kangaroo grazing pressure and weed invasion, the severely degraded state of native pastures was perpetuated by rabbits. The effect of rabbits on native pasture can be recorded in a simple manner that is suitable for identifying density–damage relationships in the presence of other herbivores and changes over time. This method is seen as particularly useful in setting target densities below which rabbits must be managed to maintain native plant communities and ecosystem function in southern Australia. It may also be useful to demonstrate rabbits’ impacts in other regions, including optimum densities for plant biodiversity benefits in their native European range.

Mitigating impacts of weeds and kangaroo grazing following prescribed fire in a Banksia woodland

SummaryBanksia woodlands are renowned for their flammability and prescribed fire is increasingly employed to reduce the risk of wildfire and to protect life and property, particularly where these woodlands occur on the urban interface. Prescribed fire is also employed as a tool for protecting biodiversity assets but can have adverse impacts on native plant communities. We investigated changes in species richness and cover in native and introduced flora following autumn prescribed fire in a 700‐hectare Banksia/Tuart (Eucalyptus gomphocephala) woodland that had not burnt for more than 30 years. Effectiveness of management techniques at reducing weed cover and the impacts of grazing by Western Grey Kangaroo (Macropus fuliginosus) postfire were also investigated. Thirty plots were established across a designated burn boundary immediately before a prescribed fire in May 2011, and species richness and cover were measured 3 years after the fire, in spring of 2013. Fencing treatments were established immediately following the fire, and weed management treatments were applied annually in winter over the subsequent 3 years. Our results indicate that autumn prescribed fire can facilitate increases in weed cover, but management techniques can limit the establishment of targeted weeds postfire. Postfire grazing was found to have significant adverse impacts on native species cover and vegetation structure, but it also limited establishment of some serious weeds including Pigface (Carpobrotus edulis). Manipulating herbivores in time and space following prescribed fire could be an important and cost‐effective way of maintaining biodiversity values.

Bringing forward the benefits of coarse woody debris in ecosystem recovery under different levels of grazing and vegetation density

Restoration projects often do not effectively restore some key biological resources that take time, often centuries, to accumulate. Such resources are often characteristic of ‘natural’ ecosystems and are critical to successful ecosystem recovery. Deadwood or ‘coarse woody debris’ (CWD) is one such example. Coarse woody debris is depauperate in many of the world’s ecosystems due to stand structural simplification through vegetation clearing, logging and grazing. The lag time in the natural accumulation of CWD can be a major barrier to their effective ecological restoration in the short term. We examined the effect of experimentally adding CWD, in four different treatments, on reptile abundance in temperate woodlands in south-eastern Australia – one of the most highly degraded vegetation types on the continent. We then investigated the influence that varying grazing pressure and vegetation density had on those effects. We examined three key questions: (1) Does the addition of CWD change overall reptile abundance over a 4year period? (2) Does existing vegetation density or kangaroo grazing effect reptile response? (3) Is there evidence of high order interaction effects between CWD, kangaroo grazing and vegetation density on reptile response? Adding CWD increased reptile abundance significantly after only 4years. The spatial pattern of CWD distribution also significantly affected reptile abundance. The location where CWD was added also was important, with open and mid-dense vegetation gaining the highest number of small skinks compared to control sites. Reduction of grazing was the most effective way of increasing small skink abundance in high density vegetation. Open areas gained most from the addition of CWD where high kangaroo grazing occurred. We conclude that adding CWD can short-cut a 100–200year barrier to ecosystem restoration. By distributing CWD in particular patterns and places in the landscape, and in combination with different grazing levels, conservation managers can improve effectiveness of restoration programs.

Resilience of a high‐conservation‐value, semi‐arid grassland on fertile clay soils to burning, mowing and ploughing

AbstractIn grassland reserves, managed disturbance is often necessary to maintain plant species diversity. We carried out experiments to determine the impact of fire, kangaroo grazing, mowing and disc ploughing on grassland species richness and composition in a nature reserve in semi‐arid eastern Australia. Vegetation response was influenced by winter–spring drought after establishment of the experiments, but moderate rainfall followed in late summer–autumn. Species composition varied greatly between sampling times, and the variability due to rainfall differences between seasons and years was greater than the effects of fire, kangaroo grazing, mowing or disc ploughing. In the fire experiment, species richness and composition recovered more rapidly after spring than autumn burning. Species richness and composition were similar to control sites within 12 months of burning and mowing, suggesting that removal of the dominant grass canopy is unnecessary to enhance plant diversity. Two fires (separated by 3 years) and post‐fire kangaroo grazing had only minor influence on species richness and composition. Even disc ploughing caused only a small reduction in native richness. The minor impact of ploughing was explained by the small areas that were ploughed, the once‐off nature of the treatment, and the high degree of natural movement and cracking in these shrink‐swell soils. Recovery of the composition and richness of these grasslands was rapid because of the high proportion of perennial species that resprout vegetatively after fire and mowing. There appears to be little conservation benefit from fire, mowing or ploughing ungrazed areas, as we could identify no native plant species dependent on frequent disturbance for persistence in this grassland community. However, the ability of the Astrebla‐ and Dichanthium‐dominated grasslands to recover quickly after disturbance, given favourable seasonal conditions, suggests that they are well adapted to natural disturbances (e.g. droughts, fire, flooding and native grazing).

A physiological assessment of the use of water point closures to control kangaroo numbers

Controlling kangaroo grazing pressure in national parks without harvesting or culling presents a significant challenge. Fencing off waterpoints is often tried or contemplated as a control measure, but its success obviously depends upon the extent to which kangaroos require access to discrete sources of drinking water. To assess the necessity for red kangaroos to supplement dietary water intake under different conditions by drinking free water, we followed changes in diet and in forage water and energy content as severe drought deepened at Idalia National Park in central Queensland from February to July 2002, the driest of 13 years for which records exist. Animals smaller than 15 kg in February and 25 kg in April did not need free water, but larger individuals needed to drink throughout the period. By July all animals needed to drink. The influence of body size arises because water requirements scale almost proportionally with body mass (M0.92) while energy requirements scale with a lower exponent (M0.74). Because of the sexual dimorphism in red kangaroos, adult females are therefore better able than adult males to survive water shortage. The results help define the constraints that physiological capabilities confer upon the usefulness of fencing off water points to control kangaroos. Smaller (younger) males and females could tolerate dry, cool conditions without drinking, even in this very dry year, but kangaroos of all body sizes needed to drink as the drought became more severe. The effectiveness of water closure will therefore depend on what forage is available, will target larger animals selectively, and will be most effective in semiarid areas like Idalia National Park in very dry years and late in the dry season when temperatures are rising and water requirements increase because of additional requirements for thermoregulation.